1. Field of the Invention
The present invention is directed to the field of internal combustion engine fuel delivery and metering systems generally. In particular, the present invention is directed to that portion of the above-noted field which is concerned with the delivery and metering of a liquid fuel into an air stream to provide a combustible air/fuel mixture for an internal combustion engine. More particularly still, the present invention is directed to that portion of the above-noted field which is concerned with the delivery and metering into an air stream of a fuel which is a liquid at standard temperature and pressure (STP) but which has been vaporized prior to mixture with the air stream. More particularly still, the present invention is directed to that portion of the above-noted field which is concerned with the vaporization of a vaporized liquid fuel for mixture with a stream of air in order to establish a combustible air/fuel mixture. More particularly still, the present invention is directed to that portion of the above-noted field which is concerned with the vaporization of a liquid fuel for an internal combustion engine under conditions in which the engine itself is not capable of generating substantial quantities of heat. More particularly still, the present invention is directed to that portion of the above-noted field which is concerned with the provision of an electrically operated liquid fuel vaporizer for providing quantities of vaporized liquid fuel sufficient to initiate and sustain engine operation during that time period when engine operation does not generate sufficient quantities of heat, as a combustion by-product, to be useful in vaporizing a liquid fuel.
2. Description of the Prior Art
It is well known in the prior art to provide a fuel in liquid form to a moving air stream for delivery to the combustion chambers of an internal combustion engine. The prior art systems generally have utilized mechanical or electromechanical fuel delivery and metering apparatus to provide metered quantities of liquid fuel in proximity to, and in some cases into, the combustion chambers of an internal combustion engine. The prior art has also taught that a quantity of liquid fuel may be added to a quantity of moving air upstream from, and for ultimate delivery to, a plurality of combustion chambers through a plurality of intake manifold conduits. The advent of federally mandated internal combustion engine exhaust emission standards has resulted in the investigation of techniques to substantially reduce the quantity of pollutants produced by an internal combustion engine. One technique proposed to reduce the quantity of atmospheric pollutants generated by an internal combustion engine has been to prevaporize the liquid fuel prior to delivery to the air stream. The basis of this proposal is the improved ability to control, from cylinder-to-cylinder within any one internal combustion engine, the air/fuel ratio of the combustion mixture. To the extent that the air/fuel ratio may be more accurately controlled, the ability to implement techniques for the reduction of atmospheric pollutants generated by the internal combustion engine may be increased.
The prior art contains a substantial number of suggestions directed to the vaporization of a liquid fuel for use in a fuel delivery system for an internal combustion engine. However, the prior art has failed to address the consideration of the vaporization of a liquid fuel for start-up of the internal combustion engine and has also failed to address the consideration of vaporization of a liquid fuel in quantities sufficient to sustain engine operation during the early phases of engine operation when the heat generated by the engine is insufficient to promote vaporization of a liquid fuel. It is therefore a specific object of the present invention to provide an auxiliary heater apparatus for converting a liquid fuel to a vapor in quantities sufficient to initiate and sustain engine operation during those phases of engine operation when the heat generated by the engine is insufficient to vaporize the liquid fuel. More particularly still, it is an object of the present invention to provide such a device which may reliably generate substantial quantities of liquid fuel vapor within a short time period after initiation of heating. More particularly still, it is an object of the present invention to provide such a device which will not create a hazard to the engine or to any automotive vehicle with which the engine is associated. More particularly still, it is an object of the present invention to provide such a device which includes overtemperature protection as a safeguard to prevent the device from generating quantities of heat in excess of that actually required to generate the desired quantities of vaporized liquid fuel. It is a further and specific object of the present invention to provide such a device which may be powered by the vehicle electrical system and which may be rendered operative only during those time periods when the auxiliary heater device is required as a liquid fuel vapor generator.